PHP: Ensures that ExitStatus error thrown my Emscripten has a stack t…

…race attached (#470)

## Description

Overrides Emscripten's default ExitStatus object which gets thrown on
failure. Unfortunately, the default object is not a subclass of Error
and does not provide any stack trace.

This is a deliberate behavior on Emscripten's end to prevent memory
leaks after the program exits. See:

emscripten-core/emscripten#9108

In case of WordPress Playground, the worker in which the PHP runs will
typically exit after the PHP program finishes, so we don't have to worry
about memory leaks.

As for assigning to a previously undeclared ExitStatus variable here,
the Emscripten module declares `ExitStatus` as `function ExitStatus`
which means it gets hoisted to the top of the scope and can be
reassigned here – before the actual declaration is reached.

If that sounds weird, try this example:

```js
ExitStatus = () => { console.log("reassigned"); }
function ExitStatus() {}
ExitStatus();
// logs "reassigned"
```

## Testing instructions

Confirm the CI tests passed

Related: #416
cc @wojtekn

packages/php-wasm/compile/Dockerfile

@@ -973,7 +973,8 @@ RUN ls /root/output/
 #     fi
 
 # Postprocess the build php.js module:
-COPY ./build-assets/append-before-return.js /root/append-before-return.js
+COPY ./build-assets/esm-prefix.js /root/esm-prefix.js
+COPY ./build-assets/esm-suffix.js /root/esm-suffix.js
 RUN \
     # Figure out the target file names and URLs
         # The .js and .wasm filenames should reflect the build configuration, e.g.:
@@ -1039,16 +1040,16 @@ RUN \
     # Turn the php.js file into an ES module
         # Manually turn the output into a esm module instead of relying on -s MODULARIZE=1.
         # which pollutes the global namespace and does not play well with import() mechanics.
-        echo "export const dependenciesTotalSize = $FILE_SIZE; " >> /root/output/php-module.js && \
         if [ "$EMSCRIPTEN_ENVIRONMENT" = "node" ]; then \
             echo "const dependencyFilename = __dirname + '/$WASM_FILENAME'; " >> /root/output/php-module.js; \
         else \
             echo "import dependencyFilename from './$WASM_FILENAME'; " >> /root/output/php-module.js; \
         fi; \
-        echo " export { dependencyFilename }; export function init(RuntimeName, PHPLoader) {" >> /root/output/php-module.js && \
+        echo " export { dependencyFilename }; " >> /root/output/php-module.js && \
+        echo "export const dependenciesTotalSize = $FILE_SIZE; " >> /root/output/php-module.js && \
+        cat /root/esm-prefix.js >> /root/output/php-module.js && \
         cat /root/output/php.js >> /root/output/php-module.js && \
-        cat /root/append-before-return.js >> /root/output/php-module.js && \
-        echo " return PHPLoader; }" >> /root/output/php-module.js && \
+        cat /root/esm-suffix.js >> /root/output/php-module.js && \
         \
         # Remove the old php.js file
         rm /root/output/php.js && \

packages/php-wasm/compile/build-assets/esm-prefix.js

@@ -0,0 +1,37 @@
+export function init(RuntimeName, PHPLoader) {
+    /**
+     * Overrides Emscripten's default ExitStatus object which gets
+     * thrown on failure. Unfortunately, the default object is not
+     * a subclass of Error and does not provide any stack trace.
+     * 
+     * This is a deliberate behavior on Emscripten's end to prevent
+     * memory leaks after the program exits. See:
+     * 
+     * https://github.com/emscripten-core/emscripten/pull/9108
+     * 
+     * In case of WordPress Playground, the worker in which the PHP
+     * runs will typically exit after the PHP program finishes, so
+     * we don't have to worry about memory leaks.
+     * 
+     * As for assigning to a previously undeclared ExitStatus variable here,
+     * the Emscripten module declares `ExitStatus` as `function ExitStatus`
+     * which means it gets hoisted to the top of the scope and can be
+     * reassigned here – before the actual declaration is reached.
+     * 
+     * If that sounds weird, try this example:
+     * 
+     * ExitStatus = () => { console.log("reassigned"); }
+     * function ExitStatus() {}
+     * ExitStatus();
+     * // logs "reassigned"
+     */
+    ExitStatus = class PHPExitStatus extends Error {
+        constructor(status) {
+            super(status);
+            this.name = "ExitStatus";
+            this.message = "Program terminated with exit(" + status + ")";
+            this.status = status;
+        }
+    }
+
+    // The rest of the code comes from the built php.js file and esm-suffix.js

packages/php-wasm/compile/build-assets/append-before-return.js → packages/php-wasm/compile/build-assets/esm-suffix.js

@@ -19,3 +19,8 @@ if (PHPLoader.debug && typeof Asyncify !== "undefined") {
         return originalHandleSleep(startAsync);
     }
 }
+
+return PHPLoader;
+
+// Close the opening bracket from esm-prefix.js:
+}

packages/php-wasm/node/public/php_5_6.js

@@ -1,6 +1,43 @@
-export const dependenciesTotalSize = 10176855; 
 const dependencyFilename = __dirname + '/php_5_6.wasm'; 
- export { dependencyFilename }; export function init(RuntimeName, PHPLoader) {
+ export { dependencyFilename }; 
+export const dependenciesTotalSize = 10176855; 
+export function init(RuntimeName, PHPLoader) {
+    /**
+     * Overrides Emscripten's default ExitStatus object which gets
+     * thrown on failure. Unfortunately, the default object is not
+     * a subclass of Error and does not provide any stack trace.
+     * 
+     * This is a deliberate behavior on Emscripten's end to prevent
+     * memory leaks after the program exits. See:
+     * 
+     * https://github.com/emscripten-core/emscripten/pull/9108
+     * 
+     * In case of WordPress Playground, the worker in which the PHP
+     * runs will typically exit after the PHP program finishes, so
+     * we don't have to worry about memory leaks.
+     * 
+     * As for assigning to a previously undeclared ExitStatus variable here,
+     * the Emscripten module declares `ExitStatus` as `function ExitStatus`
+     * which means it gets hoisted to the top of the scope and can be
+     * reassigned here – before the actual declaration is reached.
+     * 
+     * If that sounds weird, try this example:
+     * 
+     * ExitStatus = () => { console.log("reassigned"); }
+     * function ExitStatus() {}
+     * ExitStatus();
+     * // logs "reassigned"
+     */
+    ExitStatus = class PHPExitStatus extends Error {
+        constructor(status) {
+            super(status);
+            this.name = "ExitStatus";
+            this.message = "Program terminated with exit(" + status + ")";
+            this.status = status;
+        }
+    }
+
+    // The rest of the code comes from the built php.js file and esm-suffix.js
 var Module = typeof PHPLoader != "undefined" ? PHPLoader : {};
 
 var moduleOverrides = Object.assign({}, Module);
@@ -7041,7 +7078,7 @@ DNS.address_map.addrs.localhost = '127.0.0.1';
  * so that it can be inspected later.
  */
 PHPLoader.debug = 'debug' in PHPLoader ? PHPLoader.debug : true;
-if (PHPLoader.debug) {
+if (PHPLoader.debug && typeof Asyncify !== "undefined") {
     const originalHandleSleep = Asyncify.handleSleep;
     Asyncify.handleSleep = function (startAsync) {
         if (!ABORT) {
@@ -7050,4 +7087,8 @@ if (PHPLoader.debug) {
         return originalHandleSleep(startAsync);
     }
 }
- return PHPLoader; }
+
+return PHPLoader;
+
+// Close the opening bracket from esm-prefix.js:
+}

packages/php-wasm/node/public/php_7_0.js

@@ -1,6 +1,43 @@
-export const dependenciesTotalSize = 10390258; 
 const dependencyFilename = __dirname + '/php_7_0.wasm'; 
- export { dependencyFilename }; export function init(RuntimeName, PHPLoader) {
+ export { dependencyFilename }; 
+export const dependenciesTotalSize = 10390259; 
+export function init(RuntimeName, PHPLoader) {
+    /**
+     * Overrides Emscripten's default ExitStatus object which gets
+     * thrown on failure. Unfortunately, the default object is not
+     * a subclass of Error and does not provide any stack trace.
+     * 
+     * This is a deliberate behavior on Emscripten's end to prevent
+     * memory leaks after the program exits. See:
+     * 
+     * https://github.com/emscripten-core/emscripten/pull/9108
+     * 
+     * In case of WordPress Playground, the worker in which the PHP
+     * runs will typically exit after the PHP program finishes, so
+     * we don't have to worry about memory leaks.
+     * 
+     * As for assigning to a previously undeclared ExitStatus variable here,
+     * the Emscripten module declares `ExitStatus` as `function ExitStatus`
+     * which means it gets hoisted to the top of the scope and can be
+     * reassigned here – before the actual declaration is reached.
+     * 
+     * If that sounds weird, try this example:
+     * 
+     * ExitStatus = () => { console.log("reassigned"); }
+     * function ExitStatus() {}
+     * ExitStatus();
+     * // logs "reassigned"
+     */
+    ExitStatus = class PHPExitStatus extends Error {
+        constructor(status) {
+            super(status);
+            this.name = "ExitStatus";
+            this.message = "Program terminated with exit(" + status + ")";
+            this.status = status;
+        }
+    }
+
+    // The rest of the code comes from the built php.js file and esm-suffix.js
 var Module = typeof PHPLoader != "undefined" ? PHPLoader : {};
 
 var moduleOverrides = Object.assign({}, Module);
@@ -7022,7 +7059,7 @@ DNS.address_map.addrs.localhost = '127.0.0.1';
  * so that it can be inspected later.
  */
 PHPLoader.debug = 'debug' in PHPLoader ? PHPLoader.debug : true;
-if (PHPLoader.debug) {
+if (PHPLoader.debug && typeof Asyncify !== "undefined") {
     const originalHandleSleep = Asyncify.handleSleep;
     Asyncify.handleSleep = function (startAsync) {
         if (!ABORT) {
@@ -7031,4 +7068,8 @@ if (PHPLoader.debug) {
         return originalHandleSleep(startAsync);
     }
 }
- return PHPLoader; }
+
+return PHPLoader;
+
+// Close the opening bracket from esm-prefix.js:
+}

packages/php-wasm/node/public/php_7_1.js

@@ -1,6 +1,43 @@
-export const dependenciesTotalSize = 10583885; 
 const dependencyFilename = __dirname + '/php_7_1.wasm'; 
- export { dependencyFilename }; export function init(RuntimeName, PHPLoader) {
+ export { dependencyFilename }; 
+export const dependenciesTotalSize = 10583885; 
+export function init(RuntimeName, PHPLoader) {
+    /**
+     * Overrides Emscripten's default ExitStatus object which gets
+     * thrown on failure. Unfortunately, the default object is not
+     * a subclass of Error and does not provide any stack trace.
+     * 
+     * This is a deliberate behavior on Emscripten's end to prevent
+     * memory leaks after the program exits. See:
+     * 
+     * https://github.com/emscripten-core/emscripten/pull/9108
+     * 
+     * In case of WordPress Playground, the worker in which the PHP
+     * runs will typically exit after the PHP program finishes, so
+     * we don't have to worry about memory leaks.
+     * 
+     * As for assigning to a previously undeclared ExitStatus variable here,
+     * the Emscripten module declares `ExitStatus` as `function ExitStatus`
+     * which means it gets hoisted to the top of the scope and can be
+     * reassigned here – before the actual declaration is reached.
+     * 
+     * If that sounds weird, try this example:
+     * 
+     * ExitStatus = () => { console.log("reassigned"); }
+     * function ExitStatus() {}
+     * ExitStatus();
+     * // logs "reassigned"
+     */
+    ExitStatus = class PHPExitStatus extends Error {
+        constructor(status) {
+            super(status);
+            this.name = "ExitStatus";
+            this.message = "Program terminated with exit(" + status + ")";
+            this.status = status;
+        }
+    }
+
+    // The rest of the code comes from the built php.js file and esm-suffix.js
 var Module = typeof PHPLoader != "undefined" ? PHPLoader : {};
 
 var moduleOverrides = Object.assign({}, Module);
@@ -7007,7 +7044,7 @@ DNS.address_map.addrs.localhost = '127.0.0.1';
  * so that it can be inspected later.
  */
 PHPLoader.debug = 'debug' in PHPLoader ? PHPLoader.debug : true;
-if (PHPLoader.debug) {
+if (PHPLoader.debug && typeof Asyncify !== "undefined") {
     const originalHandleSleep = Asyncify.handleSleep;
     Asyncify.handleSleep = function (startAsync) {
         if (!ABORT) {
@@ -7016,4 +7053,8 @@ if (PHPLoader.debug) {
         return originalHandleSleep(startAsync);
     }
 }
- return PHPLoader; }
+
+return PHPLoader;
+
+// Close the opening bracket from esm-prefix.js:
+}

packages/php-wasm/node/public/php_7_2.js

@@ -1,6 +1,43 @@
-export const dependenciesTotalSize = 10993354; 
 const dependencyFilename = __dirname + '/php_7_2.wasm'; 
- export { dependencyFilename }; export function init(RuntimeName, PHPLoader) {
+ export { dependencyFilename }; 
+export const dependenciesTotalSize = 10993354; 
+export function init(RuntimeName, PHPLoader) {
+    /**
+     * Overrides Emscripten's default ExitStatus object which gets
+     * thrown on failure. Unfortunately, the default object is not
+     * a subclass of Error and does not provide any stack trace.
+     * 
+     * This is a deliberate behavior on Emscripten's end to prevent
+     * memory leaks after the program exits. See:
+     * 
+     * https://github.com/emscripten-core/emscripten/pull/9108
+     * 
+     * In case of WordPress Playground, the worker in which the PHP
+     * runs will typically exit after the PHP program finishes, so
+     * we don't have to worry about memory leaks.
+     * 
+     * As for assigning to a previously undeclared ExitStatus variable here,
+     * the Emscripten module declares `ExitStatus` as `function ExitStatus`
+     * which means it gets hoisted to the top of the scope and can be
+     * reassigned here – before the actual declaration is reached.
+     * 
+     * If that sounds weird, try this example:
+     * 
+     * ExitStatus = () => { console.log("reassigned"); }
+     * function ExitStatus() {}
+     * ExitStatus();
+     * // logs "reassigned"
+     */
+    ExitStatus = class PHPExitStatus extends Error {
+        constructor(status) {
+            super(status);
+            this.name = "ExitStatus";
+            this.message = "Program terminated with exit(" + status + ")";
+            this.status = status;
+        }
+    }
+
+    // The rest of the code comes from the built php.js file and esm-suffix.js
 var Module = typeof PHPLoader != "undefined" ? PHPLoader : {};
 
 var moduleOverrides = Object.assign({}, Module);
@@ -7023,7 +7060,7 @@ DNS.address_map.addrs.localhost = '127.0.0.1';
  * so that it can be inspected later.
  */
 PHPLoader.debug = 'debug' in PHPLoader ? PHPLoader.debug : true;
-if (PHPLoader.debug) {
+if (PHPLoader.debug && typeof Asyncify !== "undefined") {
     const originalHandleSleep = Asyncify.handleSleep;
     Asyncify.handleSleep = function (startAsync) {
         if (!ABORT) {
@@ -7032,4 +7069,8 @@ if (PHPLoader.debug) {
         return originalHandleSleep(startAsync);
     }
 }
- return PHPLoader; }
+
+return PHPLoader;
+
+// Close the opening bracket from esm-prefix.js:
+}